The feasibility of modifying Australian timber utility poles so as to reduce the severity of vehicular impact while maintaining the conductor cables' integrity was first investigated by a simplified mathematical model which showed promising results. Several modification schemes were then subjected to impact tests with a specially-built scale model test facility. The test results indicate that the recommended modification for all timber pole configurations consists of two layers of crossed-holes connected by vertical slots. In the case of two-crossarm poles a second pole modification consisting of crossed-holes just below the lower crossarm is recommended. No upper pole modification is required for the single-crossarm pole configuration. Instead, the pole and crossarm strip easily away from the conductors by breaking the cable tie wires. The installation of restraining cables between poles for all configurations will prevent secondary collisions between the vehicle and breakaway pole for all but the lowest speed impacts.
Abstract